Liquid crystals and semiconductors are generally produced by using the photolithography technique. The photolithography technique includes a process step of removing an unnecessary resist (photosensitive agent) by dissolving the resist with a resist remover (cleaning agent).
Various kinds of the resist remover used in the process step have been invented. However, all the inventions have been made in view of the initial peeling property and the anticorrosion property to a wiring material, and are not developed in view of the length of service life.
A resist remover is researched and developed for enhancing the quality and productivity of liquid crystals and semiconductors, and for producing a liquid crystal panel in particular, a resist remover of a mixed system of a polar solvent, such as dimethylsulfoxide or diethylene glycol monobutyl ether, and monoethanolamine has been widely used.
After using the resist remover to a certain extent, the resist is dissolved in the resist remover, and the capability of removing the resist is deteriorated due to the increased concentration thereof. Accordingly, the current situation is that a part or the whole amount thereof is periodically withdrawn from the apparatus for exchanging.
Upon exchanging the resist remover, however, it is necessary to stop the removing apparatus once, which disadvantageously lower the productivity of liquid crystal panels. The used resist remover thus withdrawn is recovered and regenerated through distillation, and the distillation residue is discarded. The regeneration through distillation requires energy, and upon discarding the residue, a part of the remover liquid contained in the residue is disadvantageously lost.
Accordingly, it is demanded to develop a resist remover that maintains a sufficient removing capability even in a state where a resist is dissolved therein at a high concentration and has a long service life.
In a removing apparatus used in the production of liquid crystal panels, specifically, the panel is cleaned with a remover, and then rinsed with water in a state where the resist remover is attached to the surface of the panel. At this time, the resist remover attached to the surface of the panel is discarded in the form of rinsing waste water as a loss (entrainment loss). In addition to the entrainment loss, there is a loss that is eliminated as vapor or mist from the removing apparatus (vapor or mist loss). The remover is continuously used while replenishing the loss amount, and thereby the concentration of the resist in the resist remover in the removing apparatus reaches a certain equilibrium concentration. The equilibrium concentration varies depending on the tank capacity of the removing apparatus, the size of the liquid crystal panels, and the like, and is generally from 0.9 to 2% by mass.
Accordingly, such a resist remover is demanded that provides a sufficient removing capability even in a state where the resist is dissolved therein at a concentration of approximately from 0.9 to 2% by mass.
As a technique for extending the service life of the remover liquid, Patent Documents 1 and 2 disclose an example of addressing by machine, in which an on-line analyzer is provided for maintaining the compositional concentration of the resist remover. In the case where the technique is practiced, however, the cost of the apparatus is increased, and the service life essentially depends on the capability as a remover of the resist remover liquid.
Patent Document 3 discloses the technique, in which a device for regenerating the remover liquid online is attached to a resist removing apparatus. In the case where the technique is practiced, however, the apparatus can be operated for a prolonged period of time, but there are problems that the regeneration of the remover requires energy, a large-scale apparatus is required, and the regeneration cost is increased.